Method for manufacturing polycarbonate resin

Abstract

This invention relates to a method for preparing a capped polycarbonate resin, comprising the steps of: a) reacting a dihydroxy compound and a carbonate in a melt, optionally in the presence of an transesterification catalyst, thereby forming a polycarbonate in a molten phase having free hydroxyl terminal groups; and b) reacting the polycarbonate in the molten phase with a capping agent to produce a capped polycarbonate resin, wherein the capping agent comprises an anhydride, and wherein the polycarbonate in the molten phase is subjected to at least partially vacuum after being combined with the capping agent. The invention also relates to capped polycarbonate resins obtained or obtainable by this method. Furthermore, the invention relates to molding articles comprising or composed of such capped polycarbonate resins, and methods for manufacturing such molding articles.

Description

Technical Field

[0001] This invention relates to a method for manufacturing polycarbonate resins using a melt transesterification process. Background Technology

[0002] Polycarbonate resins are well-known materials that typically exhibit good mechanical and optical properties. Typical applications include optical media carriers, glass windows, extruded sheets, lenses, and water bottles. Polycarbonate resins are generally manufactured using two different technologies. In the first technology, known as the interface technology or interface method, phosgene is reacted with one or more bisphenols, such as bisphenol A (BPA), in the liquid phase. The other well-known technology used to manufacture polycarbonate resins is the so-called melt technology, sometimes also referred to as melt transesterification or melt polycondensation. In the melt technology or melt method, a dihydroxy compound (typically bisphenol, more typically BPA) is reacted with a carbonate (typically diaryl carbonate, more typically diphenyl carbonate (DPC)) in the molten phase. Transesterification catalysts are typically used to achieve the desired molecular weight and to facilitate the polycondensation reaction.

[0003] In the interfacial approach, polycarbonate is dissolved in a solvent such as dichloromethane, chlorobenzene, or a mixture of both, and the method includes several purification steps before the polycarbonate resin is separated and provided in powder or granule form. This means that typical interfacial polycarbonate resins are essentially free of catalysts or catalyst residues and contain only small amounts of other impurities.

[0004] In the melt process, the polycarbonate resin is obtained directly from the final reactor, and purifying this polycarbonate resin is impossible, or at least economically infeasible. This means that any contaminants present in the raw materials or generated during the polymerization process, as well as additional catalysts or catalyst residues, remain in the obtained polycarbonate resin. Furthermore, polycarbonate resins obtained via the melt transesterification process are known to differ structurally from interfacial polycarbonate resins. First, melt-bound polycarbonate resins typically have a minimal amount of branching caused by the Fries and / or Kolbe-Schmidt rearrangement mechanism, which is generally not present in interfacial polycarbonate resins. Second, melt-bound polycarbonate resins typically have a much higher number of phenolic hydroxyl end groups, while polycarbonate resins obtained via the interfacial process are typically capped and have up to 150 ppm, preferably up to 50 ppm, more preferably up to 10 ppm of phenolic hydroxyl end groups.

[0005] Compared to interface-prepared polycarbonate resins, polycarbonate resins prepared by reacting dihydroxy compounds such as bisphenols (e.g., bisphenol A, "BPA") and carbonates such as diaryl carbonates (e.g., diphenyl carbonate, "DPC") in a melt transesterification process typically contain a significant level of uncapped chains (7-50%). These uncapped chains can have a significant impact on the resulting properties of the polycarbonate resin, and therefore in many cases it is desirable to include capping agents with higher capping efficiency than DPC during or after the polymerization reaction, which terminate the uncapped chains.

[0006] Known capping agents are typically derivatives of phenol's carbonate or ester forms, or even the monohydroxyphenol itself. Well-known examples include p-cumylphenol (PCP), 4-tert-butylphenol (TBP), and 4-octylphenol (OP).

[0007] US 2003 / 144456A1 discloses a method for end-capping polycarbonate resin in a molten transesterification reaction to produce polycarbonate resin, wherein p-cumylphenol (PCP) is used as the end-capping agent.

[0008] US6706846B2 discloses a method for end-capping a polycarbonate resin, comprising the steps of: processing a mixture of a polycarbonate having free hydroxyl end groups and an end-capping agent in a molten transesterification reaction to prepare the polycarbonate resin, wherein the end-capping agent comprises a mixture of (a) at least one class of symmetrically activated aromatic carbonate and (b) at least one class of optionally substituted phenol, whereby the end-capping agent reacts with at least some of the free hydroxyl end groups of the polycarbonate to produce the end-capped polycarbonate resin.

[0009] The process requires end-capped polycarbonate resins containing small amounts of starting material dihydroxy compounds such as bisphenols, such as bisphenol A (BPA). End-capped polycarbonate resins are also required, wherein the molecular weight (MW) is maintained at an acceptable minimum. A method for manufacturing end-capped polycarbonate resins with a high end-capping percentage is also required. Summary of the Invention

[0010] Therefore, one object of the present invention is to provide a melt transesterification method for resulting in improved polycarbonate resins.

[0011] Another object of the present invention is to provide a method for molten transesterification of a polycarbonate resin containing a small amount of a starting material dihydroxy compound such as bisphenol, for example bisphenol A (BPA), while the melt transesterification (MW) is maintained at an acceptable level.

[0012] Another object of the present invention is to provide a method for manufacturing polycarbonate resins with a high percentage of capped ends.

[0013] According to the present invention, which at least partially satisfies the foregoing objectives, the present invention relates to a method for preparing a capped polycarbonate resin, comprising the steps of: a) reacting a dihydroxy compound and a carbonate in a melt, optionally in the presence of an transesterification catalyst, thereby forming a polycarbonate in a molten phase having free hydroxyl end groups; and b) reacting the polycarbonate in the molten phase with a capping agent to produce a capped polycarbonate resin, wherein the capping agent comprises an anhydride.

[0014] Surprisingly, the use of end-capping agents containing acid anhydrides resulted in polycarbonate resins with small amounts of residual dihydroxy compounds, relatively high molecular weights, and high end-capping percentages. The high end-capping percentage led to improved water stability, color, and even potentially improved mechanical properties such as impact resistance.

[0015] The present invention also provides a method for preparing a capped polycarbonate resin, comprising the steps of: a) reacting a dihydroxy compound and a carbonate in a melt, optionally in the presence of an transesterification catalyst, thereby forming a polycarbonate in a molten phase having free hydroxyl end groups; and b) reacting the polycarbonate in the molten phase with a capping agent to produce a capped polycarbonate resin, wherein the capping agent comprises an anhydride, and wherein the polycarbonate in the molten phase is subjected to at least partially vacuum after being combined with the capping agent.

[0016] The method of the present invention includes b) reacting the polycarbonate in the molten phase with a capping agent to produce a capped polycarbonate resin, wherein the capping agent comprises an anhydride, and wherein the polycarbonate is subjected to at least partially vacuum during step b). By applying vacuum after the polycarbonate and capping agent are combined (during the reaction of the polycarbonate and the capping agent), volatile byproducts and residual dihydroxy compounds of the capping reaction can be removed.

[0017] Capping reagent

[0018] The capping agent comprises or is composed of an anhydride. For the purposes of this invention, the capping agent preferably comprises at least 50% anhydride. More preferably, the capping agent comprises at least 80% by weight, for example at least 90% by weight or 100% by weight, anhydride. The anhydride may be a single anhydride or a combination of two or more anhydrides. In one embodiment, the capping agent may also comprise other compounds besides anhydrides. Examples include phenol, p-tert-butylphenol, p-cumylphenol, octylphenol, nonylphenol, and other capping agents well known in the art.

[0019] According to the present invention, the anhydride of the capping agent reacts with the free hydroxyl end groups of the polycarbonate prepared by melt reaction. Therefore, the capped polycarbonate resin prepared by the method of the present invention contains no or substantially no anhydride end groups.

[0020] The acid anhydride is preferably selected from symmetrical or asymmetrical acyclic acid anhydrides, cyclic acid anhydrides, dianhydrides, or combinations thereof. Preferably, the acid anhydride is symmetrical.

[0021] Acid anhydrides can be noncyclic acid anhydrides according to Formula I:

[0022]

[0023] Where R 1 and R 2 Independently selected from substituted or unsubstituted straight-chain or branched C1-C20 hydrocarbon groups. In one embodiment, the hydrocarbon group is selected from alkyl, alkenyl, alkynyl, or aryl. In one embodiment, R 1 =R 2 The anhydride is a symmetrical acyclic anhydride.

[0024] Preferably, the acyclic anhydride is a symmetrical aromatic carbonate according to Formula II:

[0025]

[0026] Where R 3 The substituted group is selected from hydrogen, halogen, aryl, branched alkane, alkyne, carboxyl, and CN. For example, the phenyl group may have a halogen substituted at the meta or para position. In another example, the phenyl group may have hydrogen, aryl, branched alkane, alkyne, carboxyl, or CN substituted at the para position of the phenyl group. Acyclic anhydrides may also have one or more additional substitutions on the phenyl group, which may be related to R. 3 Same or different.

[0027] The acid anhydride may be a cyclic acid anhydride according to formula III, which is an optionally substituted phthalic anhydride:

[0028]

[0029] Where R 4 Selected from carboxyl groups and halogens.

[0030] For the purposes of this invention, the acid anhydride is preferably selected from:

[0031]

[0032]

[0033] Or a combination thereof, wherein each X is independently selected from F, Cl, Br and I, and n represents an integer from 1 to 10.

[0034] In one embodiment, the acid anhydride is benzoic anhydride according to formula 1.

[0035] In one embodiment, the acid anhydride has no more than two acid anhydride functional groups, that is, the acid anhydride has one acid anhydride functional group or two acid anhydride functional groups.

[0036] Preferably, the capping agent is added in an amount such that the molar ratio of the anhydride to the free hydroxyl end group in the capping agent is 0.1 to 10, more preferably 0.5 to 10, more preferably 1.6 to 3.0, and more preferably 2.0 to 3.0.

[0037] The amount of the capping agent to be added and mixed is, for example, 0.5-10% by weight based on the weight of polycarbonate, such as 1-4% by weight. The inventors have found that if the amount of capping agent is too high, this can lead to byproducts such as acid remaining in the polycarbonate, resulting in undesirable effects. For this reason, the inventors have also found it advantageous to perform the capping online before converting the polycarbonate into flakes, powders, or granules. Too low an amount generally will not produce the desired effect.

[0038] For the purposes of this invention, the acid anhydride preferably has a purity of at least 95%, preferably at least 98%.

[0039] raw materials

[0040] Commercial melt polycarbonates are typically manufactured based on a dihydroxy compound and a carbonate. The dihydroxy compound can be, for example, a dihydroxy compound having a triphenylamine structure, as described in EP0610912, but is typically a bisphenol. The carbonate can be a diaryl carbonate or a dialkyl carbonate, typically a diaryl carbonate.

[0041] Specifically, the dihydroxy compound is BPA and the carbonate is DPC. However, the invention is not limited to these starting materials; other bisphenols or carbonates may be used as is or in combination. For example, the invention also relates to a method in which the dihydroxy compound comprises BPA and another type of bisphenol. The carbonate is preferably DPC, but so-called activated carbonates, such as ester-substituted diaryl carbonates disclosed in US2008 / 0004417, may also be used. Preferably, the polycarbonate produced according to the invention is obtained by reacting BPA and DPC as the only monomers.

[0042] Therefore, preferably, the dihydroxy compound comprises or is composed of bisphenol, and / or the carbonate comprises or is composed of diaryl carbonate. More preferably, the dihydroxy compound comprises or is composed of bisphenol A (BPA), and / or the carbonate comprises or is composed of diphenyl carbonate (DPC). Most preferably, the dihydroxy compound is composed of bisphenol A (BPA) and the carbonate is composed of diphenyl carbonate (DPC).

[0043] Melt transesterification methods typically do not include purification steps for the obtained polycarbonate, similar to purification steps performed in interfacial methods. Therefore, the purity of the raw materials affects the quality level of the obtained polycarbonate.

[0044] Preferably, the bisphenol, especially BPA, has a purity of at least 99.3% by weight, preferably at least 99.5% by weight or at least 99.9% by weight.

[0045] Moreover, the diaryl carbonate, especially DPC, has a purity of at least 98.5% by weight, preferably at least 98.6% by weight or at least 99.0% by weight.

[0046] catalyst

[0047] There are no limitations on the catalyst used in the method according to the invention, and any catalyst commonly known for transesterification reactions to produce polycarbonate can be used. Therefore, the catalyst can be a so-called α-catalyst, a so-called β-catalyst, or a combination of both.

[0048] Suitable examples of α-catalysts and β-catalysts are described on page 15, lines 1–28 and on page 13, lines 11–14, lines 34 of WO2020074983A1, respectively, the description of which is incorporated herein by reference.

[0049] An α-catalyst is an alkali-containing catalyst that comprises a source of one or both of alkali metal ions and alkaline earth metal ions. Sources of these ions may include alkaline earth metal hydroxides, such as magnesium hydroxide and calcium hydroxide. Sources of alkali metal ions may include alkali metal hydroxides, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and combinations comprising two or more of the foregoing. Examples of alkaline earth metal hydroxides are calcium hydroxide, magnesium hydroxide, and combinations comprising two or more of the foregoing.

[0050] Other possible sources of alkaline earth metals and alkali metal ions include salts of carboxylic acids (such as sodium acetate) and derivatives of ethylenediaminetetraacetic acid (EDTA) (such as tetrasodium EDTA and disodium magnesium EDTA), as well as combinations comprising at least one of the foregoing. For example, a basic catalyst may comprise one or more alkali metal salts of carboxylic acids, one or more alkaline earth metal salts of carboxylic acids, or combinations comprising at least one of the foregoing. In another example, the basic catalyst comprises Na₂MgEDTA or a salt thereof.

[0051] Alkaline catalysts may also or alternatively comprise one or more salts of non-volatile inorganic acids. For example, an alkaline catalyst may comprise one or more salts of non-volatile inorganic acids, such as NaH₂PO₃, NaH₂PO₄, Na₂HPO₃, KH₂PO₄, CaH₂PO₄, Ca₂HPO₄, and combinations comprising two or more of the foregoing. Alternatively or additionally, an alkaline catalyst may comprise one or more mixed alkali metal salts of phosphoric acid, such as NaKHPO₄, CaNaHPO₄, CaKHPO₄, and combinations comprising two or more of the foregoing. An alkaline catalyst may comprise KNaHPO₄, wherein the molar ratio of Na to K is 0.5 to 2.

[0052] α catalysts typically provide 1 × 10⁻⁶ of the dihydroxy compound used per mole. -8 Up to 1×10 -2 moles, specifically 1 × 10 -7 Up to 1×10 -4 The amount of metal hydroxide used is measured in moles.

[0053] Preferably, the transesterification catalyst used in the method according to the invention comprises an α catalyst and the amount of α catalyst is such that 2 × 10⁻⁶ per mole of dihydroxy compound provides α catalyst. -7 Up to 6×10 -7 200 to 600 ppb of metal hydroxides.

[0054] As described elsewhere, step a) of the method of the present invention may involve a monomer mixing stage, an oligomerization stage, and a polymerization stage, and the end-capping agent may be added after the oligomerization reactor, for example, between the final oligomerization reactor and the first polymerization reactor, in the first polymerization reactor, or between the first and second polymerization reactors, or in the second polymerization reactor (which may be the final polymerization reactor).

[0055] It was found that the addition of the end-capping agent to the final polymerization reactor resulted in a decrease in the molecular weight of the resulting final-capped polycarbonate resin. It was also found that a higher amount of the catalyst used prevented this decrease in the molecular weight of the final-capped polycarbonate resin.

[0056] Therefore, in some preferred embodiments of the invention, the end-capping agent is added to the final polymerization reactor, and the transesterification catalyst used in the method according to the invention comprises an α-catalyst and the amount of the α-catalyst is such that 2 × 10⁻⁶ per mole of dihydroxy compound is provided. -7 Up to 6×10 -7 200 to 600 ppb of metal hydroxides.

[0057] Catalyst quencher

[0058] Alpha catalysts are transesterification catalysts, which are typically more thermally stable than β catalysts; therefore, almost all α catalysts (e.g., greater than 80% by weight, especially greater than 90% by weight) withstand polymerization processes. Consequently, this catalyst can be used to catalyze additional and generally undesirable reactions downstream of the polymerization process, such as in extruders or even in any downstream processing step, such as injection molding. Therefore, catalyst deactivators or quenchers are typically added at the desired stage of the polymerization process.

[0059] Preferably, the method includes combining the polycarbonate in the molten phase with a quenching agent to at least partially deactivate the transesterification catalyst, wherein the combination with the quenching agent occurs upstream of the combination with the capping agent.

[0060] Quenchers preferably include sulfonates, such as formula R 8 SO3R 9 Alkyl sulfonates, wherein R 8 Hydrogen, C1-C 12 Alkyl, C6-C 18 Aryl or C7-C 19 alkylaryl, and R 9 For C1-C 12 Alkyl, C6-C 18 Aryl or C7-C 19 Alkyl aryl. Examples of alkyl sulfonates include benzene sulfonates, p-toluene sulfonates, methyl benzene sulfonates, ethyl benzene sulfonates, n-butyl benzenesulfonate, octyl benzenesulfonate and phenyl benzenesulfonate, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, n-butyl p-toluenesulfonate, octyl p-toluenesulfonate and phenyl p-toluenesulfonate. Sulfonates may include alkyl toluenesulfonates, such as n-butyl toluenesulfonate.

[0061] Based on the total weight of polycarbonate, a quencher can be added in amounts of 1-10 ppm. The exact amount of quencher depends on the amount of α-catalyst added during the process and should be sufficient to deactivate at least 90% of the remaining catalyst. To this extent, the amount of quencher added is equivalent to 0.1 to 75 times, specifically 0.5 to 30 times, more specifically 1 to 20 times, or even more specifically 1.5 to 10 times, the neutralizing equivalent of the catalyst used. The quencher can be part of a quencher composition that further comprises a liquid carrier such as a solvent or a solid carrier such as a polymer, preferably polycarbonate.

[0062] The preferred quencher is butyl toluenesulfonate.

[0063] Methods / facilities

[0064] Melt transesterification reaction

[0065] This invention is not limited by how the melt transesterification reaction is carried out or how the facilities for polymerization are configured. Typically, the method includes a monomer mixing stage, an oligomerization stage, and a polymerization stage. During polymerization, the temperature is typically increased, the pressure is typically decreased, and the molecular weight of the polycarbonate increases.

[0066] Given the increased viscosity of the polymer during formation, higher temperatures and lower pressures are required to promote the polymerization reaction and effectively remove byproducts of the condensation reaction, typically phenol.

[0067] The facility for manufacturing polycarbonate can be part of an integrated site, and BPA and DPC and / or other raw materials can be directly sourced from other facilities or units on-site, producing the monomers in solid or molten form. However, the invention is not limited to such embodiments; raw materials such as BPA and DPC can also be obtained from external sources and added to the monomer mixing stage using appropriate feeding equipment and after applying any optional pretreatment such as melting, filtration, purification, solvent removal, etc. For example, BPA and DPC can be provided in tanks or bulk containers, and fed directly or indirectly to one or more monomer mixing units.

[0068] In the monomer mixing stage, the raw materials (typically BPA and DPC) are mixed in a molten state. Optionally, a certain amount of β-catalyst may be added in this stage. The monomer mixing stage is preferably carried out at a temperature of 100 to 250°C, specifically 150 to 200°C, and more specifically 160 to 185°C. The pressure in the monomer mixing stage is preferably substantially atmospheric pressure, such as 900 to 1100 mbar.

[0069] The α catalyst is preferably added downstream of the monomer mixing unit, and can be added, for example, upstream of one or more oligomerization and / or polymerization reactors and / or directly to the one or more oligomerization and / or polymerization reactors.

[0070] The oligomerization stage is preferably carried out in two steps, wherein in the first step the temperature is 230 to 260°C and the pressure is 140 to 250 mbar, and wherein in the second step the temperature is higher than that of the first step, at 260 to 290°C and the pressure is 10 to 50 mbar. However, the invention is not limited to two steps, and any number between 1 and 6, such as 2, 3, 4 or 5 oligomerization steps, can be used.

[0071] Based on the determination of polystyrene standards, the weight-average molecular weight of the oligomers obtained from the oligomerization stage is preferably up to 20,000, and more preferably 8,000 to 12,000 Daltons.

[0072] The polymerization stage is preferably carried out in two steps, wherein in the first step, the temperature is 280 to 315°C and the pressure is 1 to 5 mbar, and wherein in the second step, the temperature is 280 to 315°C and the pressure is 0.3 to 5.0 mbar. However, the invention is not limited to two steps, and any number between 1 and 6, such as 2, 3, 4 or 5 polymerization steps, can be used.

[0073] In one embodiment, the obtained polycarbonate in the molten phase has at least 10 ppm of free hydroxyl end groups, preferably 10 ppm to 1500 ppm of free hydroxyl end groups. This can be achieved through... 31 P NMR was used to determine the amount of free hydroxyl terminal groups.

[0074] React polycarbonate in the molten phase with a capping agent.

[0075] There are no particular restrictions on the methods of adding end-capping agents to polycarbonate.

[0076] For example, end-capping agents can be added to polycarbonate in batch or continuous reactor systems. The end-capping agent can be appropriately added to molten polycarbonate and mixed in a static mixer.

[0077] According to the present invention, after the desired molecular weight has been reached during polymerization, i.e. after the dihydroxy compound reacts with the carbonate and forms a polycarbonate polymer, a capping agent containing an anhydride is added to the polycarbonate in the molten phase.

[0078] In one embodiment, a capping agent is added after the oligomerization reactor, for example, between the final oligomerization reactor and the first polymerization reactor, in the first polymerization reactor, or between the first and second polymerization reactors.

[0079] End-capping agents can be added to the final polymerization reactor.

[0080] Polycarbonate typically has a weight of 35,000-45,000 MwPS (g / mol) before entering the first polymerization reactor.

[0081] At the outlet of the final polymerization reactor, based on the weight of the polycarbonate, the polycarbonate preferably contains up to 50 ppm, more preferably up to 10 ppm, of residual dihydroxy compounds or residual bisphenol A.

[0082] Another possibility is to add the end-capping agent in a later stage. After the final polymerization reactor, molten polycarbonate at a temperature substantially the same as that of the final reactor can be fed into a unit where the end-capping agent and other optional components can be added, such as a static mixer and / or a melt mixing device, preferably an extruder.

[0083] End-capping agents can be added to the melt mixing apparatus, for example, at the feed section of the melt mixing apparatus corresponding to the section that feeds the melt from the final polymerization reactor to the extruder. However, end-capping agents can also be added at the transfer line connected to the feed section of the melt mixing apparatus. End-capping agents can be added at a single location or at different locations, such as at different sections of the extruder or at both the feed section and the transfer line of the melt mixing apparatus.

[0084] In addition to or as an alternative to adding end-capping agents to the final polymerization reactor or melt mixing unit, end-capping agents can also be added to static mixers. For example, end-capping agents can be added to a static mixer that receives molten polycarbonate from the final reactor, and the mixture from the static mixer can then be fed to an extruder.

[0085] In one embodiment, no end-capping agent is added to the melt mixing apparatus, for example, no end-capping agent is added to the extruder.

[0086] When a quencher is added to the polymer melt, it is preferable to add the capping agent before the quenching of the polycarbonate. Therefore, it is preferable to add the capping agent upstream of the addition of the catalyst quencher. Thus, in some preferred embodiments, the catalyst quencher is added to the polycarbonate in the molten phase after step b). The catalyst quencher is not added upstream of the addition of the capping agent to the polycarbonate in the molten phase obtained in step a). The capping agent is added to the polycarbonate in the molten phase obtained in step a), a vacuum is applied, and then the catalyst quencher is applied. The inventors have found that this configuration is advantageous for maintaining catalyst activity and utilizing its reactivity to maintain MW at a desired level.

[0087] According to the invention, after the polycarbonate in the molten phase is combined with the end-capping agent, the stream is subjected to a vacuum, at least partially. This can be done using a vacuum component provided in a first or second polymerization reactor or melt-mixing apparatus. The vacuum can be, for example, in the range of 0.5-5 mbar, such as 1-3 mbar. This is particularly advantageous because applying a vacuum after combining (and mixing) the polycarbonate in the molten phase with the end-capping agent can be used to influence the viscosity and molecular weight (MW) of the polycarbonate resin. When a vacuum is applied directly after combining (and mixing) the polycarbonate in the molten phase with the end-capping agent (in the same vessel), this ensures sufficient residence time and activity of the catalyst. The vacuum also allows for the removal of volatile byproducts of the end-capping reaction, such as acids generated from anhydrides. It should be recognized that when a vacuum is applied in the melt-mixing apparatus, only a portion of the polycarbonate obtained by step b) can be under vacuum.

[0088] Additives may optionally be added, for example, to melt mixing apparatus and / or static mixers. Suitable examples of optional additives include one or more of the following: impact modifiers, flow modifiers, fillers, reinforcing agents (e.g., glass fiber or talc), antioxidants, heat stabilizers, light stabilizers, UV light stabilizers and / or UV absorbing additives, plasticizers, lubricants, mold release agents, particularly glyceryl monostearate, pentaerythritol tetrastearate, glyceryl tristearate, stearyl stearate, antistatic agents, antifogging agents, antimicrobial agents, colorants (e.g., dyes or pigments), flame retardants, said flame retardants may be combined with or not combined with anti-dripping agents, said anti-dripping agents such as polytetrafluoroethylene (PTFE) or PTFE-encapsulated styrene-acrylonitrile copolymers. The invention is not limited in the type and amount of additives, and embodiments in which the additives of the examples above are not added are also possible.

[0089] Although branching agents can be added to the mixture, it is preferable not to add them.

[0090] melt filter

[0091] Preferably, after the polycarbonate in the molten phase is combined with the end-capping agent, the stream is passed through a melt filter. The melt filter is designed to remove any particulate matter or gel from the stream.

[0092] Melt filters can have pore sizes ranging from, for example, 2.5 to 60 micrometers.

[0093] Finally, the polycarbonate in the molten phase is passed through a die to form one or more strands, which are then cooled and cut into pellets.

[0094] Figure 1 This is an illustrative and non-limiting example of a facility for manufacturing polycarbonate according to the present invention.

[0095] BPA and DPC are added to monomer mixing unit 10 as streams A and B1, respectively. The ratio of DPC to BPA in the monomer mixing unit is kept constant. β-catalyst is added to monomer mixing unit 10 via stream C. Monomer mixing unit 10 is equipped with a suitable stirrer to ensure a homogeneous mixture within the unit. Monomer mixing unit 10 is typically maintained at a temperature of 160 to 185°C and a pressure of 200-300 mbar above atmospheric pressure. The stream exiting monomer mixing unit 10 is fed to the first oligomerization reactor 20. For process flexibility, an additional amount of DPC may be added as stream B2. α-catalyst is added as stream D. The monomer mixture is then fed to the oligomerization reactor 20 in the oligomerization stage.

[0096] Oligopolymer reactor 20 operates at a temperature of 230 to 260°C and a pressure of 140 to 250 mbar. The overhead stream, containing phenolic byproducts and optionally monomers or other low molecular weight reaction products, is removed via stream 70 and fed to column 50, where phenol is separated from the stream. The phenol is then removed via top stream E for further purification and / or use, while the bottom stream is returned to reactor 20 as stream 71. In an alternative embodiment, stream 70 is purified elsewhere, and no material is recycled to oligopolymer reactor(s) 20, 21.

[0097] The mixture exiting reactor 20 is fed into a second oligomerization reactor 21 for further reaction. The second oligomerization reactor 21 is operated at a temperature of 260 to 290°C and a pressure of 10 to 50 mbar. The phenolic byproduct is removed from the second reactor 21 as stream E.

[0098] Oligopolymer reactors 20 and 21 constitute the oligopolymerization stage, producing a stream of polycarbonate oligomers which is fed into a first polymerization reactor 30 and then into a second polymerization reactor 31. Reactor 30 operates at a temperature of 280 to 315°C and a pressure of 1 to 5 mbar. The stream from the first polymerization reactor 30 is then fed into the second polymerization reactor 31, which operates at a temperature of 280 to 315°C and a pressure of 0.3 to 5.0 mbar. The temperature in reactor 31 is typically higher than that in reactor 30, and the pressure in reactor 31 is typically lower than that in reactor 30. Similar to the oligopolymerization stage, phenolic byproducts are removed from reactors 30 and 31. Together, polymerization reactors 30 and 31 constitute the polymerization stage.

[0099] The polymer leaving the second polymerization reactor 31 is fed into the extruder 40.

[0100] A certain amount of end-capping agent can be added at the feed section of polymerization reactor 30 via feed 16a or at the feed section of polymerization reactor 31 via feed 16b. Alternatively, the end-capping agent can also be added at the feed section of extruder 40 via feed 16c, or injected into the melt stream from reactor 31, in the transfer pipe and near the feed section of the extruder.

[0101] Optionally, other additives may be added to the extruder, indicated by I. Alternatively, additives may be added at the feed section of the extruder.

[0102] A catalyst quencher is also added to the extruder to deactivate the catalyst in the molten carbonate. Alternatively, the catalyst quencher can be added to the second polymerization reactor 31. In this case, it is preferable to add the end-capping agent to the first polymerization reactor 30. To avoid ambiguity, it should be noted that the location where the catalyst quencher is added is not limited.

[0103] The stream extruded from extruder 40 is passed through melt filter 60, then extruded into strands, cooled and cut into pellets, indicated by J.

[0104] It should be noted that, although Figure 1 The polymerization reactors 30 and 31 are shown as horizontal polymerization units, but these reactors can also be vertical reactors independently, such as wire wetting fall polymerization units.

[0105] Figure 1 The method shown is presented as a single production line. However, it is possible that at any point during this method, the production line could be split into two or more parallel production lines, each operating under the same or different conditions, including monomer blend composition, temperature, pressure, residence time, etc. For example, the stream exiting oligomer reactor 21 could be split into two or more distinct streams, which would then allow each stream to be polymerized in one or more polymerization reactors under, for example, different conditions, resulting in the parallel production of different grades of polycarbonate. Another possibility is to separate the stream exiting final polymerization reactor 31 and then feed the polycarbonate streams to different extruders. Figure 1 The parallel operation of the production line (partially shown) is known to the technicians.

[0106] Apart from Figure 1 In addition to the specific configuration shown, polycarbonate can be manufactured under one or more of the following preferred conditions.

[0107] Preferably, the monomer mixing stage includes the addition of a β catalyst, wherein the β catalyst is a quaternary ammonium or quaternary phosphorus compound or a mixture thereof.

[0108] Preferably, the oligomerization stage consists of preparing polycarbonate oligomers in two oligomerization reactors, and the polymerization stage consists of preparing polycarbonate in two polymerization reactors.

[0109] In a preferred embodiment of the method of the present invention, the bisphenol is BPA, the diaryl carbonate is DPC, a β catalyst is added during the monomer mixing stage, and an α catalyst is added before feeding the monomer mixture prepared in the monomer mixing device to the first oligomerization reactor. In a preferred embodiment, the bisphenol is BPA, the diaryl carbonate is DPC, the α catalyst is NaKHPO4, and the β catalyst is tetrabutylphosphonium acetate.

[0110] The method of the present invention is preferably a continuous method.

[0111] End-capped carbonate resin

[0112] Compared to polycarbonate resins of the same nature produced under otherwise identical conditions without the addition of the end-capping agent according to the invention, the end-capped carbonate resins produced according to the invention have a smaller amount of dihydroxy compound and / or similar or higher molecular weight and / or higher end-capping level.

[0113] To avoid ambiguity, it should be noted that the carbonates obtained by the method of the present invention do not contain carbonate chains containing anhydride functional groups derived from the capping reagent. Therefore, the anhydride functional groups of the capping reagent react with the hydroxyl (terminal) groups of the carbonate and are thus not incorporated into the polymer chain in this manner.

[0114] The capped carbonate resin may have a weight-average molecular weight, for example, from 30,000 to 70,000 g / mol, such as from 30,000 to 50,000 g / mol or from 50,000 to 70,000 g / mol, as determined by GPC based on polystyrene standards.

[0115] In some embodiments, the capped carbonate resin has a weight-average molecular weight of at least 36,000 g / mol, as determined by GPC based on polystyrene standards.

[0116] Preferably, the capped polycarbonate resin has a capping level of at least 60%, more preferably 65 to 95%, and even more preferably 70 to 95%, wherein the capping level is defined as the percentage of polycarbonate chain ends that are not hydroxyl groups. Thus, a polycarbonate resin with a 60% capping level means that 40% of the polycarbonate chain ends are phenolic OH end groups, typically generated from bisphenol A monomers. The remaining 60% of the end groups do not contain OH end groups and can be phenolic (typically derived from diphenyl carbonate) or correspond to one or more capping reagent molecules.

[0117] Calculate the end cap level using the following formula:

[0118]

[0119] Where %EC is the end-capping level, ppmOH is the amount of hydroxyl end groups in parts per million by weight, and Mn is the number-average molecular weight of polycarbonate based on polycarbonate standards.

[0120] Therefore, the end-capping level is defined as the molar percentage of non-hydroxyl end groups in the end-capped polycarbonate resin, and can be calculated from the amount of terminal OH groups and the number-average molecular weight (Mn) in the end-capped polycarbonate resin.

[0121] Based on the total amount of end groups, the amount of chain ends capped with the capping reagent is preferably at least 40%.

[0122] End-capped carbonate resins can have a branching degree of 200–4000 ppm, for example 500–2000 ppm, resulting from the Fries (or Kolbe-Schmidt) rearrangement reaction. The branching degree is commonly referred to as the amount of Fries branching. Methods for determining the amount of Fries branching are known to those skilled in the art and typically involve methanololysis of the polycarbonate resin followed by HPLC to identify the total amount of Fries structure. Alternatively, NMR techniques can be used to determine the type and amount of branched structures, such as the corresponding amounts of linear and branched Fries structures.

[0123] It should be understood that some amount of residual material used during the process of manufacturing the end-sealed polycarbonate resin may remain in the end-sealed polycarbonate resin obtained by the method. Therefore, as used herein, the term "polycarbonate resin" should be understood to include not only polycarbonate molecules but also residual material.

[0124] In some embodiments, the dihydroxy compound is bisphenol A, and the amount of residual bisphenol A in the end-capped polycarbonate resin is at most 50 ppm, preferably at most 25 ppm, more preferably at most 10 ppm, and most preferably at most 5 ppm, based on the weight of the end-capped polycarbonate resin.

[0125] In some embodiments, the amount of hydroxyl end groups in the polymer chain is at most 1100 ppm, preferably at most 500 ppm, and more preferably at most 450 ppm, based on the weight of the end-capped polycarbonate resin.

[0126] In one embodiment, at least 70%, preferably 80-90%, of the added end-capping agent is incorporated into the end-capped polycarbonate resin.

[0127] The amount of residual dihydroxy compounds in end-sealed polycarbonate resins can be determined by the following methods.

[0128] Sample preparation:

[0129] Dissolve 0.5 g of polycarbonate in 5 ml of dichloromethane (DCM), and precipitate the polycarbonate with 10 ml of methanol. Filter the solution into an LC sampling vial.

[0130] Analytical techniques:

[0131] High-performance liquid chromatography-diode array detector (HPLC-DAD).

[0132] Column: Zorbax Eclipse XDB-C18 4.6 x 75 mm 3.5 um.

[0133] Column temperature: 35℃.

[0134] Wavelength: 280nm (BPA).

[0135] polycarbonate composition

[0136] The present invention further provides a polycarbonate composition comprising an end-capped polycarbonate resin and additives.

[0137] Suitable examples of additives include one or more of the following: impact modifiers, flow modifiers, fillers, reinforcing agents (e.g., glass fiber or talc), antioxidants (primary and / or secondary antioxidants), heat stabilizers, light stabilizers, UV light stabilizers and / or UV absorbing additives, plasticizers, lubricants, mold release agents, particularly glyceryl monostearate, pentaerythritol tetrastearate, glyceryl tristearate, stearyl stearate, antistatic agents, antifogging agents, antimicrobial agents, colorants (e.g., dyes or pigments), flame retardants, said flame retardants may or may not be combined with anti-dripping agents, said anti-dripping agents being, for example, polytetrafluoroethylene (PTFE) or PTFE-encapsulated styrene-acrylonitrile copolymers. The invention is not limited in the type and amount of additives.

[0138] In some embodiments, the polycarbonate composition comprises at least one of a primary antioxidant and a secondary antioxidant.

[0139] In some embodiments, the polycarbonate composition comprises the polycarbonate according to the invention and at least one of a primary antioxidant and a secondary antioxidant.

[0140] The present invention further provides thermoplastic compositions comprising an end-capped polycarbonate resin according to the invention or a polycarbonate composition according to the invention and at least one additional polymer, preferably selected from the group consisting of: polycarbonate-polysiloxane copolymers, polycarbonate-polyester copolymers, polyesters, polyolefins, acrylonitrile / butadiene / styrene copolymers, methyl methacrylate / butadiene / styrene copolymers, styrene / butadiene / styrene copolymers (SBS), styrene / ethylene-butene / styrene copolymers (SEBS), styrene / ethylene-propylene / styrene copolymers (SEPS), styrene / acrylonitrile copolymers (SAN), acrylonitrile / styrene / acrylonitrile copolymers (ASA), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), unsaturated polyesters (UPES), polyamides (PA), thermoplastic polyurethanes (TPU), polystyrene (PS), high-impact polystyrene (HIPS), polyvinyl chloride (PVC), polyetherimide, and polysulfone. The amount of polycarbonate relative to the thermoplastic composition may be, for example, 5 to 95% by weight, 50 to 95% by weight, or 55 to 95% by weight.

[0141] The thermoplastic composition according to the invention can be prepared, for example, by melt mixing an end-capped polycarbonate resin according to the invention or a polycarbonate composition according to the invention with at least one other polymer.

[0142] The present invention further provides molded articles comprising, or composed of, end-sealed polycarbonate resin, polycarbonate composition, or thermoplastic composition according to the present invention, according to the present invention.

[0143] The present invention further provides a method for manufacturing molded articles, the method comprising molding an end-sealed polycarbonate resin according to the present invention, a polycarbonate composition according to the present invention, or a thermoplastic composition according to the present invention.

[0144] The invention will now be further illustrated based on the following non-limiting embodiments.

[0145] Use such as Figure 1 The equipment shown in the diagram continuously produces end-sealed polycarbonate resin.

[0146] BPA and DPC were introduced into a monomer mixing unit maintained at a temperature of 170°C and a pressure of approximately 1050 mbar. A β-catalyst of 50 μmol tetrabutylphosphonium acetate (TBPA) / mol BPA was also added.

[0147] The monomer mixture was then introduced into a first oligomerization reactor operating at a temperature of 250-270°C and a pressure of 155-190 mbar. The initial DPC / BPA ratio (molar ratio) was adjusted to 1.020-1.045 with additional DPC, and a certain amount of NaKHPO4 was added as an α catalyst. The carbonate oligomers formed in the first oligomerization reactor were fed into a second oligomerization reactor operating at a temperature of 275-295°C and a pressure of 10-37 mbar.

[0148] The resulting carbonate oligomers are then introduced into a first polymerization reactor operating at a temperature of 295-300°C and a pressure of 2.0-4.0 mbar.

[0149] 30 g of the material produced from the first polymerization reactor was combined with a capping agent, namely anhydride (solid powder), such that the molar ratio of anhydride to OH content in the polycarbonate was maintained at 1:1 or 3:1. This composition was mixed in a glass reactor and heated to 300°C for 25 minutes while maintaining a pressure of 1 mBar in the reaction vessel. After the reaction, the polycarbonate mixture was separated and characterized using standard analytical techniques, such as gel permeation chromatography (GPC) to determine MW (using polystyrene standards), HPLC to determine Fries branching content (using Fries standards), and HPLC to determine unreacted BPA residues. NMR spectroscopy was used to determine the incorporation of anhydride into the polycarbonate backbone.

[0150] The structure of the end-capped polycarbonate resin was obtained by NMR analysis.

[0151] The amount of residual BPA was determined by HPLC.

[0152] The amount of residual benzoic acid was determined by HPLC.

[0153] MW was determined using GPC based on polystyrene standards.

[0154] The end-cap level %EC is determined as follows:

[0155]

[0156] Where %EC is the end-capping level, ppmOH is the amount of hydroxyl end groups in parts per million by weight, and Mn is the number-average molecular weight of the end-capped polycarbonate resin based on the polycarbonate standard.

[0157] pass 31 The amount of hydroxyl-terminated groups was determined by NMR. For this purpose, 200 mg of PC sample was dissolved in 2 mL of CDCl3 (deuterated chloroform) solvent containing Cr(acac)3 and m-cresol as internal standards. A few drops of 1,2-phenylenephosphine chloride (PPC) were added and mixed, resulting in derivatization of the OH-terminated groups. NMR spectra were recorded on an Agilent 400 MHz spectrometer equipped with a probe operated at 25 °C.

[0158] pass 1 1H NMR spectroscopy was used to determine the amount of a specific end-capping agent containing anhydride incorporated into end-capped polycarbonate resins. In CDCl3 1 ¹H NMR spectroscopy was used to calculate the incorporation of the end-capping reagent. Concentrations were calculated based on the amount of BPA or on the internal standard m-cresol. The mass of the new endcap was adopted as follows: 121 g / mol in the case of end-capping reagent derived from benzoic anhydride, and 85.08 g / mol in the case of end-capping reagent derived from methacrylic anhydride.

[0159]

[0160]

[0161] In addition, the percentage of “new capping” was calculated, which is the percentage of capping produced by the addition of a capping agent containing an anhydride. Typically, a portion of the capping is produced by phenyl carbonate capping from the formulation itself (BPA+DPC in these examples), and an additional portion is produced by the addition of a capping agent. The “new capping” percentage specifies the latter portion.

[0162] Table 1 provides an overview of the different embodiments. CE1 is a comparative embodiment in which the same protocol is followed, but without the addition of capping reagents.

[0163] Table 1: Overview of Examples

[0164]

[0165] Table 2 summarizes the results obtained. The results include the weight-average molecular weight (MwPS), number-average molecular weight (MnPS), and number-average molecular weight (MnPC) of polycarbonate resins capped with polystyrene standards. The polydispersity index (PDI) can be used as a measure of the breadth of molecular weight distribution: the higher the PDI, the wider the molecular weight distribution. PDI is the ratio of MwPS to MnPS. Table 2 also shows the amount of hydroxyl terminal groups (OH), the capping level (total EC%, calculated as described above), the amount of residual BPA, the amount of capping agent incorporated into the capped polycarbonate resin, and the new capping level (new capping%, as described above).

[0166] Table 2: Results

[0167]

[0168] It should be noted that the amount of residual benzoic acid was measured, but it was below the detection limit for all (comparative) examples.

[0169] As shown in Table 2, using a capping agent containing an anhydride resulted in a higher capping percentage than when no anhydride was used, and the amount of residual dihydroxy compound (BPA) was significantly reduced. These effects were most pronounced when the ratio of benzoic anhydride to hydroxyl end groups was 3:1. The last two columns of Table 2 confirm that additional capping was indeed achieved by adding a capping agent.

[0170] Meanwhile, as can be seen from Table 2, the MW of the obtained end-capped polycarbonate resin is still relatively high and remains at an acceptable level compared with the comparative example without anhydride.

[0171] Table 3 shows the amount of end-capping agent incorporated into the polycarbonate chain via the reaction of acid anhydrides with hydroxyl end groups. Using methods such as… Figure 1 The apparatus, as illustrated and described above, continuously produces the end-capped polycarbonate resins of Examples E5-E7. For all these Examples E5-E7, the polycarbonate flow rate is 65 kg / h. For all three Examples E4-E6, the end-capping agent is benzoic anhydride. Examples E4-E6 differ in the amount of end-capping agent added, and therefore in the anhydride:hydroxyl molar ratio.

[0172] For E5-E7, the amount of hydroxyl terminal groups (OH) was determined by FTIR spectroscopy. For this purpose, 500 mg of PC sample was dissolved in 10 mL of dichloromethane. Fresh, dried molecular sieves were added to the solution to remove moisture (H₂O) that might interfere with the response of the OH stretching frequency in FT-IR. The FT-IR spectra were recorded on a PerkinElmerSpectrum 100 spectrophotometer.

[0173] pass 1 The amount of a specific capping agent incorporated into the capped polycarbonate resin (“capping agent incorporation”) was determined by 1H NMR spectroscopy. The new capping level (new capping %, as described above) was then determined (not shown), and the percentage of added benzoic anhydride incorporated into the polycarbonate chain was calculated from this.

[0174] Table 3

[0175]

[0176] As can be seen from Table 3, a large amount of capping agent can be incorporated into the capped polycarbonate resin by means of the method according to the present invention.

[0177] Use such as Figure 1 The schematically illustrated apparatus continuously produces additional end-capped polycarbonate resins. Benzoic acid is added in various amounts (as shown in Table 4) between the first polymerization reactor 30 and the second polymerization reactor 31. NaKHPO4 is added as an α-catalyst in various amounts (as shown in Table 4) at the inlet of the first oligomerization reactor 10.

[0178] Table 4

[0179]

[0180] Understandably, adding benzoic acid to the final polymerization reactor results in a higher percentage of end-capping than when no anhydride is used, but also leads to a lower molecular weight of the final end-capped polycarbonate resin obtained, see CE11 and E12.

[0181] It is also understandable that using a higher amount of catalyst reduces this reduction in the molecular weight of the final capped polycarbonate resin, see CE11, E12, and E13. A higher amount of benzoic acid results in a higher capping percentage, see E13-E16.

Claims

1. A method for preparing end-capped polycarbonate resin, comprising the following steps: a) Reacting a dihydroxy compound and a carbonate in a melt, optionally in the presence of an transesterification catalyst, thereby forming a polycarbonate in the molten phase having free hydroxyl end groups; and b) Reacting the polycarbonate in the molten phase with a capping agent to produce a capped polycarbonate resin, wherein the capping agent comprises an acid anhydride. The polycarbonate in the molten phase is subjected to at least partially vacuum after being combined with the capping agent.

2. The method according to claim 1, wherein the acid anhydride is selected from symmetrical or asymmetrical acyclic acid anhydrides, cyclic acid anhydrides, dianhydrides, or combinations thereof.

3. The method according to claim 2, wherein the acid anhydride is a noncyclic acid anhydride according to formula I: Where R 1 and R 2 It is independently selected from substituted or unsubstituted straight-chain or branched C1-C20 hydrocarbon groups.

4. The method according to claim 3, wherein the acyclic anhydride is a symmetrical aromatic carbonate according to formula II: ， Where R 3 Selected from hydrogen, halogen, aryl, branched alkanes, alkynes, carboxyl groups, and CN.

5. The method according to claim 2, wherein the anhydride is a cyclic anhydride according to formula III, and the cyclic anhydride is an optionally substituted phthalic anhydride: ， Where R 4 Selected from carboxyl groups and halogens.

6. The method according to claim 1 or 2, wherein the acid anhydride is selected from the following formula: Or a combination thereof, wherein each X is independently selected from F, Cl, Br and I, and n represents an integer from 1 to 10, preferably wherein the anhydride is benzoic anhydride according to formula 1).

7. The method according to any one of the preceding claims, wherein the capping agent is added in an amount such that the molar ratio of the anhydride to the free hydroxyl terminal group in the capping agent is 0.1 to 10, preferably 0.5 to 10, more preferably 1.6 to 3.0, and more preferably 2.0 to 3.

0.

8. The method according to any one of the preceding claims, wherein the capping agent is added to a container comprising a vacuum device by which the polycarbonate in the molten phase, combined with the anhydride, is subjected at least partially to a vacuum of 0.5-5 mbar, for example, in the range of 1-3 mbar.

9. The method according to any one of the preceding claims, wherein a catalyst quencher is added to the polycarbonate in the molten phase after step b).

10. The method according to any one of the preceding claims, wherein the transesterification catalyst comprises an α catalyst, and the amount of the α catalyst is such that each mole of the dihydroxy compound provides 200-600 moles of metal hydroxide in ppb.

11. A capped polycarbonate resin obtained or obtainable by any one or more of the methods of claims 1-10, preferably wherein the amount of residual dihydroxy compound or residual bisphenol A in the capped polycarbonate resin is at most 50 ppm, preferably at most 10 ppm, based on the weight of the capped polycarbonate resin.

12. A capped polycarbonate resin obtained or obtainable by any one or more of the methods of claims 1-10, wherein the amount of hydroxyl end groups in the polymer chain is at most 1100 ppm, preferably at most 500 ppm, and more preferably at most 450 ppm based on the weight of the polycarbonate.

13. The end-capped polycarbonate resin according to claim 11 or 12, wherein the end-capped polycarbonate resin has a weight-average molecular weight of at least 36,000 g / mol, determined using GPC based on polystyrene standards.

14. The end-capped polycarbonate resin according to any one of claims 11-13, wherein the end-capped polycarbonate resin has a fries branching content of 200-4000 ppm, preferably 500-2000 ppm.

15. A molding article comprising a polycarbonate resin or a polycarbonate resin thereof that is end-capped according to any one of claims 11-14.

16. A method for manufacturing a molded article, comprising molding a polycarbonate resin with end caps according to any one of claims 11-14.

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